LESS THAN STANDARD SEPARATION AND POTENTIAL CONFLICT BETWEEN CORPORATE LTT AND UNKNOWN ACFT.

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RECEIVED AND READBACK CLRNC OF 180 DEG TO INTERCEPT LOC 16 AT KHPN TO CROSS LEASA INTXN AT OR ABOVE 5000'. LEVELING AT 5000 ABOUT 1.5 NM OUTSIDE OF LEASA; A DIFFERENT CTLR ON SAME FREQ ADVISED 'LTT; INCREASE YOUR RATE OF DSCNT BELOW 5000; TFC AT 5000'; EBND AT 2 O'CLOCK AND 2 MI.' WE CONTINUED DSCNT; WERE IMMEDIATELY CLRED LEFT TO 090 DEG; AND THEN PRIOR TO REACHING 090 DEG; FURTHER LEFT TO 190 DEG. DURING THIS TURN; I QUERIED THE CTLR ABOUT SOME FINAL ALT TO LEVEL OFF AT. WE WERE ABOUT 4500' AT THE TIME. I TOLD HIM WE HAD THE UNDERSTANDING WE WERE GOING TO 2000'. HE CANCELLED THE APCH CLRNC; 'IF YOU EVER HAD ONE;' REASSIGNED US LEFT TO 130 DEG TO INTERCEPT THE LOC AT 3000' AND PROCEED INBND. TWO THINGS: I CANNOT FORCE CTLRS TO RESPOND TO READBACKS WHICH MIGHT HAVE CAUGHT AN ERROR IN OUR READBACK; IF THERE WAS ONE. SECOND; I BELIEVE THERE WAS CONFUSION IN THE TRANSITION BTWN CTLRS. INTERESTINGLY ENOUGH; WE'D JUST BEEN COMPLEMENTED FOR A FINE READBACK FOR A LENGTHY CLRNC ABOUT 20 MIN PRIOR.